A cokpobatioh



Nov. 29, 1927. 1,650,995

' T. G. MARTIN AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 14, 1921 lira-fir? Tall??? 13. PU arhn llhll'lElfl Mod p yt? TALBOT G. MARTIN, O CHTLCJLGO, ILLINOIS, BY IBEEEEITE ASSIGKMEFTICEEZ Elli) AUTOMATIC ELECTRIC INC, OF CHICAGQ, ILLINOIS, A CORPQRATIUN 01E DELA- WARE.

AUTOTFATIC TELEPHQNE SYSTELIE.

Original application filed February 14, 1921, Serial No. 444,663, now Patent No. 1,583,4l8'0, dated May (l,

1926. Divided and this application filed January 25, 1926.

The present invention relates in general to an automatic telephone system and more particularly to automatic switches for use in such systen'is. As illustrated herein, the in vention is applied to an automatic switch of the type known as a selector switch, that is, one which has access to a plurality of trunk lines divided into groups and which may be numerically operated. to select a desired group oi trunk lines, and then operate automatically to select an idle trunk line in the group, extend a connection thereover, and be released when the calling party or both parties, as the case may be, restore their receivers.

In the past a selector switch of the standard type, upon being released, rotated its test wiper, along with its line wipers, back over the bank contacts of trunks passed in its hunting operation, and in rotating over busy or, grounded contacts, more especially two or more consecutive busy contacts, its test.

relay was apt to be operated, thereby under certain circumstances causing a partial or completeoperation of the rotary magnet and otherwise interfering with the normal re lease of the switch.

The object of the present invention .is to provide means for positively preventing the energization of the test relay during the release of the switch. 7 division of my application Serial No. 444,663,

filed February 14, 1921, now PatentNor The particular manner in which this and other results are accomplished will be de scribed hereinafter. reterence being had to shows theusual automatic type of substation A having" an individual line switch C of the well known plunger type individual thereto. The lineswitch C, in common with a plurality of other lineswitches is adapted to be controlled by a master switch D.

lhis application 1s a Serial No. 83,4l l l.

function ol the master switch l), is Well known. is to maintain the plungers or. all idle lineswitches opposite an idle trunk line. The trunk lines accessible to the lineswitch C and other similar lineswitchcs terminate in selector switches one oi which is shown at E. The selector ll] oi the usual Eitrow vertical and rotary type having; the usual set 0! 100 bank contacts arranged in 10 rows or levels. The levels of the selector switches lead to second selectors, repeaters, outgoing secondary lineswitches, or to con nector switches. as the case may be. The bank contacts 85-87, inclusive, accessible to theselector E, terminate in one of the above mentioned switches.

The selector switch has the usual relays, magnets and shaft oitl-nori'nal springs, and in addition has a set of off-normal springs which are controlled directlv by thedoubledog, as shown in Fig. 2. The springs make contact when the double-dog is released by the vertical magnet and break contact when the release magnet restores the doubledog to normal. These springs are also shown in my Patent No. 1,109,650, granted Sela tember l, 1914.

Having briefly described the apparatus involved in the invention, a detailed description of its operation will now be given. For this purpose it will be assumed that the subscriber at station A desires to call a subscriber in the same or another automatic exchange.

.l fhen the receiver is removed at substation A a circuit is completed for the line relay 20 over the line conductors ll and 12 in series. Upon energizing, the line relav 20 at its armature 32 completes the circuit of "the pull down winding The pull down winding upon energizing. attractsthe plunp: er arm 28 thereby forcing the springs 40- 43, inclusive, into engagement with their working contacts. The cut-oil armature 29 is also attracted by the energization of the pull down winding 25. By the engagement of sprin 4:0 and 4:8 with their working con tacts the line conductors l1 and 12 are extended by way of armatures TO and '33 and their back contacts to the upper and lower winding of the line relay 50 or" the selector E.

' llie line relay 50 is energized over lllfl line circuit of the calling subscriber and closes at its armature 60 the circuit of the slow acting release relay 51. The latter relay upon operating, at armature 62 prepares the operating circuits of the selector E and at armature 61 places ground on the release trunk conductor 63 thereby establishing a holding circuit which. extends by way of working contact of spring 41 and the said spring, and through the holding winding 26 of the line switch C to battery. The energization of the holding winding 26 serves to maintain the cut-off armature 29 and the plunger arm 28 in an operated position. It will be noted that the cut-01f armature up n operating opens the circuit of the line relay 20, and it will be understood that the circuit for the holding winding 26 was completed before the line relay 20 had time to deenergize. A branch of the holding circuit extends :by way of the private normal conductor 39 to multiply connected test contacts in the banks of connector switches which have access to the line of the substation A whereby the said line is protected from intrusion in the well known manner.

By the engagement of spring 42 with its working contact ground isplaced on the contact in the master switch bank associated with the selected trunk line whereby the master switch is caused to select another idle trunk line in the usual manner.

The calling subscriber at substation A may now operate his calling device for the first digit of his desired number. A series of interruptions are thereby produced in the circuit of the line relay 50 which deenergizes a corresponding number of times. At each retraction of its armature 60 an impulse of current is sent over the following circuit: ground by way of back contact and armature 72, armature 60 and its back contact, armature 62 and its front contact, winding of the slow acting series relay 52, and thence through the winding of the vertical magnet 55 to battery. Magnet 55 operates to raise the switch wipers 8082, inclusive, step-byst'ep until they are placed opposite the level of bank contacts in which are terminated trunk lines leading to the succeeding switches. In addition, on its first energizetion magnet 55 releases the double dog (see Fig. 2) so as to permit it to engage the switch shaft and the double dog moves the spring into engagement with its working contact. The slow acting relay 52 which is energized in series with the vertical magnet maintains its armature attracted throughout the vertical movement of the switch. Upon the first vertical step of the switch shaft a circuit is completed extending from ground on release trunk conductor 63, by way of armature 64 and its front contact, oif-normal spring 65 and its working contact, winding of the interrupter or test relay 53, working contact of spring 75 and the said spring, and back contact and armature 69 to battery. Upon energizing relay 53 at armature 67 establishes a locking circuit for itself and at armature 68 prepares the rotary magnet circuit. Upon the termination of the vertical movement of the switch the slow acting relay 52 is deencrgized and a circuit is completed extending from ground on release trunk conductor 63 by way of armature 64 and its back contact, armature 68 and its front contact, and through the winding of the rotary magnet 56 to battery. The rotary magnet 56 operates to rotate the switch wipers into engagement with the terminals of the first trunk line in the selected level and at the same time breaks the locking circuit of the interrupter relay '53 at armature 69. Relay 53 then deenergizes opening the circuit of the rotary magnet 56 which deenergiz'es also. The operation of the selector E now depends upon whether or not the trunk line with which the switch wipers -82., inclusive, are in engagement is or is not busy. If busy, there will be a grounded potential present on the test contact engaged by test wiper S1 and a circuit may be traced extend ing from the said grounded test contact by way of test wiper 81, armature 71 and its back contact, off-normal spring 65 and its working contact, through the winding of the interrupter relay 53, working contact of spring 75 and the said spring, and back contact and armature 69 to battery. The inter-' rupter relay 53 is again energized over this circuit and operates in the same manner as before to establish a locking circuit for itself at armature 67 and at armature 68 to complete the rotary magnet circuit. Magnet 56 operates to rotate the switch wipers into engagement with the bank contacts associated with the next trunk line in the selected level and to break the holding circuit of the interrupter relay 53' which deenergizes breaking the circuit of the rotary magnet which then deenergizes also. The alternate operation of the interrupter relay 53 and the rotary magnet 56 will continue until an idle trunk is found, which we will assume is the trunk line shown in the drawing terminating in bank contacts 85-87, inclusive. When this occurs there is no ground present on the test contact 36 engaged by test wiper 81 and the switching relay 54 will be no longer short circuited. A circuit may then be traced extending from ground on release trunk conductor 63, through the winding of the switching relay 54, off-normal spring 65, and its working contact, through the winding of the interrupter relay 53, working contact of spring 75 and the said spring, and back contact and armature 69 to battery. It may be stated at this point that the switching relay 54 is of comparatively high resistance and relay 53 will notoperateover the above circuit.

When the switching relay is energized, this relay at armatures and 7 3 disconnects the incoming line conductors from the wind inns of the line relay and extends them by way of wipers 80 and 82. bank contacts 85 and 87. to the trunk conductors 90 and As a further result of the energization of relay 54 a holding circuit is prepared for selector 1*) and line switch C by connecting release trunk conductor 63 to the test wiper 81 at armature 71. The succeedingswitch operates to return holdingground in the well known manner, the circuit extending by way of release trunk conductor 91, bank contact 86, test wiper 8]. armature 7'1 and its front contact, where it divides. one path extending back to the holdinp winding' of the lineswitch (l. the other through i the winding of the switching relay 54 ot the selector E. This circuit serves to maintain the switches C and E in their opera ted position.

The calling subscriber may now operate his calling device in accordance with the remaining digit or digits in the desired subscribers number and the other automatic switch or switches, as the case may be, will be operated in the usual manner to extend a connection to the desired called subscriber.

The calling and called subscribers may now converse with each other and when the conversation is completed, the calling subscriber at station A by replacing his re ceiver upon the switchhook, will cause the deenergization of the line relay of the repeater or connector switch. as the case may be. which immediately deenergizes and breaks the circuit of the slow acting release relay. The latter relay will deenera ize after a short interval and remove ground. from the release trunk conductor 91. When ground is removed from the release trunk conductor the switching relay 54 of the selector E and the holding winding of the individual lineswitch C are deenergized. Upon the deenergization of the holding winding of the lineswitch C the plunger arm and the cut-ofi armature immediately assume their normal positions.

When the switching relay 54 deenergizes, the circuit of the release magnet 57 is completed and by the operation of the release magnet 57 the double-dog is restored to normal, which operation opens springs and releases theswitch shaft. It will now be apparent that should the test wiper 81 of the selector E engage grounded test contacts upon its return there will be no circuit completed for the interrupter relay 53 as this circuit is opened by the operation of spring 75. Thus the relay 53 will not again energize and interfere with the release of the selector switch.

In the above manner all the switches' operated in the connection are restored to normal position V Having tully'described and ascertained the features of the invention, what is considered to be new and is desired'to have protected by Letters Patentwill be pointed'outin the appended claims.

\Vhat is claimed is:

1. In a telephone system, an automatic switch, trunk lines accessible thereto, means for making certain oat said trunk lines busy, a test relay for said switch, means'for operating" said switch to cause said relay to successively test said trunk lines, a circuit for said test relay including grounded contacts of busy trunk lines, a dog for holding said switch in operated position, means for operating said dog to release said switch, and contacts controlled by said dog for opening' said circuit during said release to prevent any false operation of said test relay in case a busy trunk line is encountered. during the restoration to normal.

2. In a telephone system, an automatic trunking switch for connecting the calling and called lines, a test circuit in said switch for controlling; the selection of 'idle trunk lines, a pair of contacts normally included in said test circuit, a dog for holding said switch in operated position, means for operating said dog to release said switch after the same has been operated and to open said test circuit at said contacts While the switch is being released.

8. In a telephone system, an automatic trunking switch for connecting calling and called lines, a test circuit in said switch for controlling the selection of idle trunk lines,

a pair of contacts normally included in said test circuit, means for releasing said switch when the connection is broken, and means controlled by said first means for opening said contacts while the switch is being released.

4. In a telephone system, an automatic trunking switch for connecting calling and called lines, a circuit including a test relay in said switch, and means for holding said circuit closed while said switch is hunting and for holding said circuit open while said switch is releasing.

5. In an automatic trunk hunting switch having a wiper carrying shaft, a double-dog for holding said shaft in operated position, a'vertical magnet for raising said shaft and operating said double-dog, a rotary magnet for rotating said shaft, a release magnet for releasing said double-dog and permitting said switch to restore to normal position, and a pair of contacts closed and opened responsive to the operation and the release of said double-dog, respectively.

6. In a two directive motion automatic switch, means for holding said switch in ,op-

erated position, means for operating a d switch in onedirection and operating said holding means, means for operating said switch in the second direction, means for releasingsaid holding m ans and allowing said switch. to return to normal position, a pair of contacts, and means for closing said contacts upon the operation of said holding means, and for opening said contacts upon the releasing of said holding means.

In Witness whereof, I hereunto subscribe my name this 21st day of January, A. D. 1926.

TALBOT Gr. MARTIN. 

